Craziness comes when beliefs don't match facts. And we're living in conditions that make that kind of belief possible.

Very early in his writing career, about 1940, science fiction writer Robert Heinlein outlined a “future history” around which much of his writing would revolve, extending from the mid-twentieth century to the 24th century. Much of what he outlined hasn’t come to pass, but he nailed it in one respect: We live in the “Crazy Years."

The Crazy Years, in Heinlein’s timeline, were when rapid changes in technology, together with the disruption those changes caused in mores and economics, caused society to, well, go crazy. They ran from the last couple of decades of the 20th Century into the first couple of decades of the 21st. In some of his novels set in that era — Time Enough for Love, for example — he includes random assortments of headlines that may have seemed crazy enough back then, but that seem downright tame today.

I’m not the first to make this connection — science fiction writers John C. Wright and Sarah Hoyt have remarked on it, and as Hoyt notes, “these are the Crazy Years” has become something of a stock joke among Heinlein fans.

But what does that mean? As Wright observes — invoking not only Heinlein but his contemporary A.E. Van Vogt, “craziness” comes when beliefs don’t match facts:

“Craziness can be measured by maladaptive behavior. The behavior the society uses to solve one kind of problem, when applied to an incorrect category, disorients it. When this happens the whole society, even if some members are aware of the disorientation, cannot reach the correct conclusion, or react in a fashion that preserves society from harm. As if society were a dolphin that called itself a fish: when it suffered the sensation of drowning, it would dive. But a dolphin is a mammal, a member of a different category of being. When dolphins are low on air, they surface, rather than dive. Putting yourself in the wrong category leads to the wrong behavior.”

Since these actions don’t bring about the desired result, the problems they’re intended to address continue to grow and fester. And the response, usually, is to double-down on the responses that don’t work.

Sometimes the craziness is short term, what cartoonist/author Scott Adams calls a "mass hysteria bubble." Such mass hysteria is nothing new, as the Salem Witch Trials and the Tulip Bubble illustrate. But sometimes — and I think this is now, because these are the Crazy Years — the underlying conditions work to continuously create bubbles of mass hysteria.

What are those conditions today? I think that Heinlein had it right with regard to technology and economics in general. But in particular, I think the rise of social media — and especially the widespread use of Twitter by journalists and politicians — has made things much crazier. Thanks to the ability to block or unfriend people with whom one disagrees, it’s much easier to live in a political/ideological bubble than it was even a decade ago. And my impression is that many journalists now write and tweet more to impress their peers than to serve their audiences.

And what’s the endgame? Well, this should worry people. In Heinlein’s future history, the Crazy Years ended with the rise of the Reverend Nehemiah Scudder, who established a theocratic dictatorship in the United States. Sick of the craziness, voters picked a leader who offered a stable framework, even if it was repressive.

I don’t want a Nehemiah Scudder (or alternative versions like Pol Pot or Hugo Chavez). And Hitler was a response to Germany’s own Crazy Years under the Weimar Republic. But you don’t get Hitler because of Hitler. There are always potential Hitlers out there. You get Hitler because of Weimar, and you get Weimar because the people charged with maintaining a liberal polity are too corrupt and incompetent — or crazy — to maintain a liberal polity.

If you don’t like the consequences, don’t do the thing that produces the consequences. Anything else is just crazy.

Glenn Harlan Reynolds, a University of Tennessee law professor and the author of The New School: How the Information Age Will Save American Education from Itself, is a member of USA TODAY's Board of Contributors. Follow him on Twitter: @instapundit.